Cars in, say, the 1960s were not "more reliable in general." It's not all semiconductor-related of course--they also rusted out quickly in areas that got snow--but 5 years/50K miles is about what you were looking at for vehicle lifetime. Also much lower fuel efficiency, to say nothing of lack of what we'd consider routine safety features today.
On that, Availability is the result of all the rest. With the important part of planned Availability, because that excludes stuff like planned maintenance. Arguably modern cars beat old ones in that category.
What's probably true is that older cars that aren't rusted out can probably be kept running by people with the appropriate mechanical skills even in the absence of proper factory/3rd party parts for longer than modern vehicles can. Given intact supply chains, modern vehicles are more available overall. But, to the point of the article, modern vehicles are more susceptible to lack of parts.
That being said, if I'd go on a 2k + mile trip I would put in some work to get the car fit for this. Looking at my dads VW camper, I'll just fill up drinking water, maybe gas and fuel. Without a serious amount of preventive maintenance those cars do have a tendency to break down so. I guess we are just not used to this kind cars or machinery anymore.
The chip-ification of cars has been going on for a really, really long time.
I think that is the largest appeal to me of older cars. There are only so many parts that can fail, and they are all repairable with some time and hand tools(and maybe a Haynes manual!).
(for people unfamiliar, a Haynes manual is a 3rd party manual customized for most makes/models of automobiles. It describes with pictures how to perform [almost] any repair.)
I don't remember how far my 1965 Austin Mini van had done by the time I scrapped it in 1978 but I'm quite sure it was much more than 50 k miles.
Is that true though? Average length of car ownership is at an all-time high of over 8 years. It was under 5 years just 20 years ago. Maybe length of ownership doesn't correlate to length of car life, but seems like a strong signal that car quality and lifespan is going up.
I merely added a small counter argument to the idea that cars of the period were necessarily short lived.
And you can also add laser eye and cosmetic surgery: have advanced by leaps and bounds in terms of safety and quality, while actually becoming less costly for the consumer.